Multidimensional ether sulfone oligomers

ABSTRACT

The solvent resistance of polyethersulfone oligomers is enhanced by using difunctional imidophenol end-cap monomers to provide improved crosslinking. The imidophenol monomers include two unsaturated functionalities capable of cross-linking upon thermal or chemical activation. Blends, pregregs, and composites using the novel end caps are described for linear or multidimensional polyethersulfone oligomers.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part and divisional applicationbased upon U.S. application Ser. No. 816,489 filed Jan. 6, 1986, U.S.Pat. No. 4,739,030 which was a continuation-in-part application basedupon U.S. application Ser. No. 704,475, filed Feb. 22, 1985, nowabandoned, which was a divisional application based upon U.S.application Ser. No. 505,348, filed June 17, 1983, now U.S. Pat. No.4,536,559.

TECHNICAL FIELD

The present invention relates to multidimensional oligomers and toprepregs, composites, or blends of polysulfone or polyethersulfoneoligomers that are capped with difunctional, crosslinking end-capmonomers. Blends include the oligomers and compatible noncrosslinkingpolymers.

BACKGROUND ART

Although thermoplastic resins and their applications are well known,reinforced resins are relatively new and have significant advantagesover pure, resinous composites. Fiber reinforcement toughens andstiffens the resin to produce high performance products. At the sametime, processing is not seriously hindered because the reinforced resinmaintains its thermoplastic character. For example, a sheet of fiberreinforced resin can be heated, stamped into a desired shape byappropriate dies, reheated and restamped to alter the shape. Incontrast, a thermosetting resin cannot be reshaped, once it is fullycured by heating. Thermoplastic resins, however, generally exhibit poorsolvent resistance, and this deficiency has severely limited their use.For example, reinforced thermoplastic resin circuit boards ofconventional design cannot be cleaned by solvents commonly used in themanufacture of circuit boards. Hydraulic fluids and cleaning fluids inaircraft limit adoption of conventional thermoplastic resins unlesstheir solvent resistance can be improved.

Recently, chemists have sought to synthesize oligomers for highperformance advanced composites suitable for aerospace applications.These composites should exhibit solvent resistance, be tough, impactresistant, and strong, be easy to process, and be thermoplastic.Oligomers and composites that have thermo-oxidative stability, and,accordingly can be used at elevated temperatures, are particularlydesirable.

While epoxy-based composites are suitable for many applications, theirbrittle nature and susceptibility to degradation make them inadequatefor many aerospace applications, especially those applications whichrequire thermally stable, tough composites. Accordingly, research hasrecently focused upon polyimide composites to achieve an acceptablebalance between thermal stability, solvent resistance, and toughness.The maximum use temperatures of conventional polyimide composites, suchas PMR-15, are still only about 600°-625° F., since they have glasstransition temperatures of about 690° F.

Linear polysulfone, polyether sulfone, polyester, and polyamide systemsare also known, but each of these systems fails to provide as highthermal stability as is required in some aerospace applications.

There has been a progression of polyimide sulfone compounds synthesizedto provide unique properties or combinations of properties. For example,Kwiatkowski and Brode synthesized maleic-capped, linear polyarylimidesas disclosed in U.S. Pat. No. 3,839,287. Holub and Evans synthesizedmaleic- or nadic-capped, imido-substituted polyester compositions asdisclosed in U.S. Pat. No. 3,729,446. We synthesized thermally stablepolysulfone oligomers as disclosed in U.S. Pat. No. 4,476,184 or4,536,559, and have continued to make advances withpolyetherimidesulfones, polybenzoxazolesulfones (i.e., heterocycles),polybutadienesulfones, and "star" or "star-burst" multidimensionaloligomers. We have shown surprisingly high glass transition temperaturesand desirable physical properties in many of these oligomers and theircomposites, without losing ease of processing.

Multidimensional oligomers, such as disclosed in our copendingapplication U.S. application Ser. Nos. 726,258; 810,817; and 000,605,are easier to process than many other advanced composite oligomers sincethey can be handled at lower temperatures. Upon curing, however, theunsaturated phenylimide end caps crosslink so that the thermalresistance of the resulting composite is markedly increased with only aminor loss of stiffness, matrix stress transfer (impact resistance),toughness, elasticity, and other mechanical properties. Glass transitiontemperatures above 950° F. are achievable.

Commercial polyesters, when combined with well-known diluents, such asstyrene, do not exhibit satisfactory thermal and oxidative resistance tobe useful for aircraft or aerospace applications. Polyarylesters areunsatisfactory, also, since the resins often are semicrystalline whichmakes them insoluble in laminating solvents, intractable in fusion, andsubject to shrinking or warping during composite fabrication. Thosepolyarylesters that are soluble in conventional laminating solventsremain so in composite form, thereby limiting their usefulness instructural composites. The high concentration of ester groupscontributes to resin strength and tenacity, but also makes the resinsusceptible to the damaging effects of water absorption. High moistureabsorption by commercial polyesters can lead to distortion of thecomposite when it is loaded at elevated temperature.

High performance, aerospace, polyester advanced composites, however, canbe prepared using crosslinkable, endcapped polyester imide ether sulfoneoligomers that have an acceptable combination of solvent resistance,toughness, impact resistance, strength, ease of processing, formability,and thermal resistance. By including Schiff base (--CH═N--), imidazole,thiazole, or oxazole linkages in the oligomer chain, the linear,advanced composites formed with polyester oligomers of our copendingapplication U.S. application Ser. No. 726,259 can have semiconductive orconductive properties when appropriately doped.

Conductive and semiconductive plastics have been extensively studied(see, e.g., U.S. Pat. Nos. 4,375,427; 4,338,222; 3,966,987; 4,344,869;and 4,344,870), but these polymers do not possess the blend ofproperties which are essential for aerospace applications. That is, theconductive polymers do not possess the blend of (1) toughness, (2)stiffness, (3) elasticity, (4) ease of processing, (5) impact resistance(and other matrix stress transfer capabilities), (6) retention ofproperties (over a broad range of temperatures), and (7) hightemperature resistance that is desirable on aerospace advancedcomposites. These prior art composites are often too brittle.

Thermally stable multidimensional oligomers having semiconductive orconductive properties when doped with suitable dopants are also knownand are described in our copending applications (including U.S.application Ser. No. 773,381 to Lubowitz, Sheppard, and Torre). Thelinear arms of the oligomers contain conductive linkages, such as Schiffbase (--N═CH--) linkages, between aromatic groups. Sulfone and etherlinkages are interspersed in the arms. Each arm is terminated with amono- or difunctional end cap (i.e., a radical having one or twocrosslinking sites) to allow controlled crosslinking upon heat-inducedor chemically-induced curing.

Polyamides of this same general type are described in our copendingpatent application U.S. application Ser. No. 061,938; polyetherimides,in U.S. application Ser. No. 016,703; and polyamideimides, in U.S.application Ser. No. 092,740.

SUMMARY OF THE INVENTION

Our U.S. Pat. No. 4,536,559 discloses and claims a series ofthermoplastic polyethersulfone resins that resist attack by organicsolvents because they include novel, difunctional end-cap monomers toprovide crosslinking. These resins have aromatic backbones for thermalstability and are resistant to solvents conventionally used in aerospaceapplications, such as MEK and methylene chloride. The oligomers can becrosslinked by thermal and/or chemical activation through thedifunctional end-cap monomers. The present invention relates toprepregs, composites, and blends of the oligomers.

The oligomers are generally prepared by reacting:

1) 2 moles A--OH,

2) (n+1) moles X--R--X (a dihalogen), and

3) n moles HO--R'--OH (a bisphenol),

wherein A is ##STR1## .0.=phenyl; i=1 or 2, and generally 2;

D is selected from the group consisting of: ##STR2## R₁ is lower alkyl,aryl, substituted alkyl, substituted aryl, lower alkoxy, aryloxy, ormixtures thereof (preferably lower alkyl of less than 4 carbon atoms);

G is --SO₂ --, --S--, --CH₂ --, or --O-- (preferably --CH₂ --);

j=0, 1, or 2;

X is halogen (preferably chlorine);

R is an aromatic radical;

R' is an aromatic radical;

Me=methyl;

E=allyl or methallyl; and

n is selected so that the polymer has a molecular weight between about1,000 and 40,000. The preferred molecular weight for oligomers isbetween about 5,000 and about 30,000, and more preferably between about10,000 and 20,000.

Preferably, R is selected from the group consisting of: ##STR3## whereinw=--SO₂ --, --S--, or --(CF₃)₂ C--. R' is preferably selected from thegroup consisting of: phenyl, biphenyl, or ##STR4## wherein y=--(CH₃)₂C--, --S--, --O--, --SO₂ --, and --(CF₃)₂ C--.

Substituent groups selected from the group consisting of halogen, alkylgroups having 1 to 4 carbon atoms, alkoxy groups having 1 to 4 carbonatoms, aryl, or substituted aryl may depend from the aryl groups of theoligomer backbone. While para isomerization is shown, other isomers maybe used. Substituent groups present steric hindrance problems, and,therefore, unsubstituted aryl groups are preferred.

The oligomers are generally made by (a) mixing the reactants with K₂ CO₃or another suitable buffer or "scavenger" in a suitable solvent in thepresence of an inert atmosphere, and (b) heating the mixture, ifnecessary, to react the compounds.

The imidophenol reactants are prepared by reacting a suitable anhydridewith diaminophenol in a solvent in the presence of an inert atmosphere.

Prepregs can be prepared from the oligomers, and composites from theprepregs or oligomers. Blends comprise the crosslinking oligomers andcompatible polymers. The polymer generally has a substantially identicalbackbone as the oligomer (i.e., is a similar polyethersulfone) but isnot capable of crosslinking. The blends provide improved physicalproperties having greater strength and toughness while retainingadequate solvent resistance.

Curing times are reduced, solvent resistance is improved (with adecrease in thermoplasticity), and lower temperatures can be used duringthe curing step by forming prepregs containing (1) the oligomers orblends and (2) a suitable coreactant containing comparable crosslinkingfunctionalities to those on the oligomer.

BEST MODE CONTEMPLATED FOR CARRYING OUT THE INVENTION

The difunctional imidophenol end-cap monomers are the condensationproducts of aminophenols and anhydrides. Polymers using these monomersare prepared in solvent polymerization by reacting dialcohols (i.e.,diols or bisphenols), dihalogens, and the monomers. Average formulaweights of the oligomers are controlled by controlling theconcentrations combinations of the three components.

Thus, crosslinkable oligomers with two crosslinking sites at each endare formed by reacting:

1) 2 moles A--OH,

2) n+1 moles X--R--X, and

3) n moles HO--R'--OH,

wherein A is ##STR5## wherein D is selected from the group consistingof: ##STR6## R₁ is lower alkyl, aryl, substituted alkyl, substitutedaryl, lower alkoxy, aryloxy, or mixtures thereof (preferably lower alkylof less than 4 carbon atoms);

G=--SO₂ --, --S--, --CH₂ --, or --O-- (preferably --CH₂ --);

j=0, 1, or 2;

X is halogen (preferably chlorine);

R is an aromatic radical;

R' is an aromatic radical;

Me=methyl;

E=allyl or methallyl; and

.0.=phenyl;

i=2; and

n is selected so that the polymer has a molecular weight between about1,000 and 40,000.

The resulting product has the polyether structure: ##STR7## Thisreaction is generally carried out by mixing all three compounds withNaOH, KOH, K₂ CO₃, Na₂ CO₃, NaHCO₃, KHCO₃, or mixtures thereof in asuitable solvent in the presence of an inert atmosphere and heating themixture, as necessary, to react the compounds. The reaction mixtureaccordingly is basic to avoid undesired side reactions. K₂ CO₃ is thepreferred "scavenger".

The average formula weight of the resulting oligomers ranges between1,000 and 40,000; preferably between about 5,000 and 30,000; and, morepreferably, between about 10,000 and 20,000. Within these ranges, theoligomers can be crosslinked in a curing step, such as vacuum bagging,to form thermoplastic polymers that are solvent resistant. Since uncuredoligomers are relatively soluble in conventional prepregging solvents,they can be easily processed into prepregs.

An oligomer having an average formula weight below about 1,000 undergoesexcessive crosslinking and loses its thermoplastic properties (theoligomer is thermosetting). An oligomer having an average formula weightabove about 40,000, on the other hand, has insufficient crosslinking andhas inadequate solvent resistance.

The difunctional imidophenol end-cap monomers of the present inventionusually are pure compounds, but mixtures of monomers having similar cureactivation temperatures may also be used to form oligomers having two ormore end-cap types.

The dialcohol is generally a polyaryl compound and preferably isselected from the group consisting of:

HO--Ar--OH;

HO--Ar--L--Ar'--L--Ar--OH;

HO--Ar'--L--Ar--L--Ar'--OH;

wherein L=--CH₂ --, --(CH₃)₂ C--, --(CH₃)₂ C--, --O--, --S--, --SO₂ --or --CO--; ##STR8## T and T₁ =lower alkyl, lower alkoxy, aryl, aryloxy,substituted aryl, or mixtures thereof;

q=0-4;

k=0-3; and

j=0, 1, or 2;

hydroquinone;

bisphenol A;

p, p'-biphenol

4, 4'-dihydroxydiphenylsulfide;

4, 4'-dihydroxydiphenylether;

4, 4'-dihydroxydiphenylisopropane;

4, 4'-dihydroxydiphenylhexafluoropropane;

a dialcohol having a Schiff base segment, the radical being selectedfrom the group consisting of: ##STR9## wherein R is selected from thegroup consisting of: phenyl;

biphenyl;

naphthyl; or

a radical of the general formula: ##STR10## wherein W=--CH₂ -- or --SO₂--; or a dialcohol selected from the group: ##STR11## wherein L is asdefined above; Me=CH₃ --;

m=an integer, generally less than 5, and preferably 0 or 1; and

D₁ =any of --CO--, --SO₂ --, or --(CF₃)₂ C--.

While bisphenol A is preferred (because of cost and availability), theother dialcohols can be used to add rigidity to the oligomer withoutsignificantly increasing the average formula weight, and, therefore, canincrease the solvent resistance. Random or a block copolymers arepossible.

Furthermore, the dialcohols may be selected from the dihydric phenolimide sulfone resins described in U.S. Pat. No. 4,584,364, which isincorporated by reference, or those dihydric phenols described in U.S.Pat. Nos. 3,262,914 or 4,611,048. Other suitable dialcohols aredescribed in our copending applications 016,703 and 726,258; or in U.S.Pat. Nos. 4,584,364; 4,661,604; 3,262,914; or 4,611,048.

The bisphenol may be in phenate form, or a corresponding sulfhydryl canbe used. Of course, mixtures of bisphenols and disulfhydryls can beused.

Dialcohols of the type described are commercially available. Some may beeasily synthesized by reacting dihalogen intermediate with bis-phenates,such as the reaction of 4,4'-dichlorophenylsulfone with bis(disodiumbiphenolate). Preferred dihalogens in this circumstance are selectedfrom the group consisting of: ##STR12## wherein X=halogen, preferablychlorine; and q=--S--, --SO₂ --, --CO--, --(CH₃)₂ C--, and

--(CF₃)₂ C--, and preferably either

--SO₂ -- or --CO--.

Preferred dihalogens for the ethersulfone condensation include4,4'-dichlorodiphenylsulfone, 4,4'-dichlorodiphenylthioether,4,4'-dichlorodiphenylhexafluoropropane, or mixtures thereof although thedihalogen can be selected from the group consisting of: ##STR13##

Crosslinking occurs upon heating the oligomers to about 450° F. to 700°F., with the preferred range being 500° F. to 650° F. Lower curingtemperatures may be used if coreactants are added to the oligomers. Thecoreactants also accelerate the curing reaction, increase solventresistance, and decrease the thermoplasticity of the resin.

For oligomers having maleic end-caps, A suitable coreactant is selectedfrom the group consisting of p-phenylenediamine, benzidine,4,4'-methylenedianiline, and simple diamines of the formula: H₂N--R--NH₂ wherein R is an alkyl having 2 to 6 carbon atoms, or mixturesthereof.

For oligomers containing the norbornene group, a suitable coreactant is:##STR14## wherein R is an alkyl having 2 to 6 carbon atoms or anaromatic radical such as: ##STR15## and R₁ and j are as previouslydefined.

Suitable coreactants for oligomers containing the acetylene groupinclude: ##STR16## wherein R, R₁ & j are as previously defined.

Blends can improve impact resistance of composites without causing asignificant loss of solvent resistance. The blends comprise mixtures ofone or more crosslinkable oligomer and one or more polymer that isincapable of crosslinking. Generally, the blends comprise substantiallyequimolar amounts of one polymer and one oligomer having substantiallyidentical backbones. The crosslinkable oligomer and compatible polymercan be blended together by mixing mutually soluble solutions of each.While the blend is preferably equimolar in the oligomer and polymer, theratio of the oligomer and polymer can be adjusted to achieve the desiredphysical properties.

Although the polymer in such a blend usually has the same lengthbackbone as the oligomer, the properties of the composite formed fromthe blend can be adjusted by altering the ratio of formula weights forthe polymer and oligomer. The oligomer and polymer generally havesubstantially identical repeating units, but the oligomer and polymermerely need be compatible in the solution prior to sweeping out as aprepreg. Of course, if the polymer and oligomer have identicalbackbones, compatibility in the blend is likely to occur. Blends thatcomprise relatively long polymers and relatively short oligomers (i.e.,polymers having higher average formula weights than the oligomers) priorto curing are preferred, since, upon curing, the oligomers willeffectively increase in MW by crosslinking.

In synthesizing the comparable polymers, quenching end caps can beemployed, if desired, to regulate the polymerization of the comparablepolymer, so that it has an average formula weight substantiallyidentical with the crosslinkable oligomer. For thermal stability, anaromatic compound, such as phenol or nitrobenzene, is preferred toquench the synthesis.

Solvent resistance may decrease markedly if the comparable polymer isprovided in large excess to the crosslinkable oligomer in the blend.

The blends will generally comprise a mixture of a polyethersulfoneoligomer and the same ethersulfone polymer. The polymer may, however, bea different polymer. The mixture may include several types of oligomersor several types of polymers, such as a three component mixture ofethersulfone oligomer, a ether oligomer, and an ether or ether polymer.

The blends may be semi-interpenetrating networks of the general typedescribed by Egli et al, "Semi-Interpenetrating Networks of LARC-TPI"available from NASA-Langley Research Center.

The polyethersulfones of the present invention can also be prepared byreacting the dialcohols with suitable dinitro compounds, insofar as thephenolic --OH will react with a nitro functionality to form an etherlinkage. Of course, the --OH may be in phenate form.

Prepregs of the oligomers or blends can be prepared by conventionaltechniques. While woven fabrics are the typical reinforcement, thefibers can be continuous or discontinuous (in chopped or whisker form)and may be ceramic, organic, carbon (graphite), or glass, as suited forthe desired application.

Composites can be formed by curing the oligomers or prepregs inconventional vacuum bag techniques. The oligomers can also be used asadhesives, varnishes, films, or coatings.

Multidimensional oligomers can be prepared using an aromatic hub thatincludes three or more reactive --OH, --X, or --NO₂, groups (such asphloroglucinol) with suitable dialcohols, dihalogens, and nitro orimidophenol end-cap monomers. For example, phloroglucinol can be mixedwith bisphenol A, dichlorobenzene, and 1-hydroxyphenyl-2,4-dinadimide toform a multidimensional polyether oligomer. Those skilled in the artwill understand the generality of this example with respect to theformation of corresponding multidimensional polyethersulfone oligomers.Multidimensional polymers can be prepared by replacing the crosslinkingend cap monomer with a quenching compound like phenol, chlorobenzene, ornitrobenzene.

Blends of the multidimensional oligomers and compatible polymers canalso be made.

To avoid competing reactions, the multidimensional oligomers can beformed in a stepwise reaction scheme, such as combining the hub with thedihalogen, adding the dialcohol, adding more dihalogen, and completingthe reaction by adding the imidophenol end-cap monomer.

The following examples are presented to illustrate various features ofthe invention:

EXAMPLE 1 Synthesis of 1-hydroxyphenyl-2,4-dinadimide

Under dry N₂, a slurry of 19.71 g (0.1 moles) of purified2,4-diaminophenol dihydrochloride was prepared containing 10 percentsolids in 17.39 g of N,N-dimethylacetamide (DMAC). 16.80 g (0.2 moles)dry NaHCO₃ was added. After foaming subsided, 65.61 g xylene and 32.83 g(0.2 moles) 5-norbornene 2,3-dicarboxylic anhydride were slowly added.Transferred to a Barrett trap filled with xylene, the reaction mixturewas refluxed (150° C.) until no more water was collected in the Barretttrap. The product was precipated in water, separated by filtration, andwashed.

EXAMPLE 2 Synthesis of 1-hydroxyphenyl-3,5-dinadimide

The process of Example 1 was repeated except that 0.1 moles of3,5-diaminophenol dihydrochloride was substituted for 2,4-diaminophenoldihydrochloride.

EXAMPLE 3 Synthesis of 1-hydroxyphenyl-2,4-dinadic (cap 10% excess, 20%excess K₂ CO₃, Formula weight 20,000)

In a 1000-ml resin kettle fitted with a mechanical stirrer, thermometer,condenser, Dean Stark trap, and dry N₂ purge, add 405.8 grams ofdimethylacetamide was added to 173.9 grams toluene, 5.70 grams (0.014mole) of 1-hydroxyphenyl-2,4-dinadimide (the compound of Example 1),98.35 grams (0.273 mole) of 4-chlorophenylsulfone, 60.87 grams (0.267mole) bisphenol A, and 45.25 grams potassium carbonate. Heated to 140°C., the mixture was refluxed for 72 hours, before raising thetemperature to 160°-165° C. to distill off the toluene. Refluxing at160°-165° C. continued for 1 hour after all toluene was collected. Theproduct was recovered thereafter by conventional steps.

EXAMPLE 4 Synthesis of 1-hydroxyphenyl-3,5-dinadimide (cap 10% excess,20% excess K₂ CO₃, Formula weight 20,000)

Using the procedure of Example 3, but substituting1-hydroxyphenyl-3,5-dinadimide (the compound of Example 2) for1-hydroxyphenyl-2,4-dinadimide yielded the desired product.

EXAMPLE 5 Preparation of composites

The oligomer obtained from either Example 3 or 4 was impregnated onepoxy-sized T300/graphite fabric style (Union Carbide 35 million modulusfiber 24×24 weave) by sweeping a 10 to 15% resin solids solution of theoligomer in methylene chloride into the fabric, taking care to wet thefibers as well as possible. The oligomer comprised about 38 wt. % of theresulting prepreg. After drying to less than 1 percent volatile content,the prepreg was cut into 6×6-inch pieces and stacked to form a laminatedcomposite of approximately 0.080 inch upon curing in a conventionalvacuum bag process under 100 psi in an autoclave at 625° F. for at least6 hours. The composite exhibited substantial resistance to conventionalsolvents, such as MEK and methylene chloride.

While preferred embodiments have been described, those skilled in theart will readily recognize alterations, variations, or modificationsthat might be made to the embodiments without departing from theinventive concept. The description and examples, accordingly, areintended to illustrate the invention. The claims should be construedliberally in view of the description, and should only be limited as isnecessary in view of the pertinent prior art.

We claim:
 1. A blended oligomer, comprising a crosslinking oligomerformed by the condensation of:(a) 2 moles of a crosslinkable imidophenolhaving at least two crosslinking functionalities; (b) n+1 moles of anaromatic dihalogen, and (c) n moles of an aromatic bisphenoland acompatible polymer, wherein the imidophenol has the formula Y_(i)--.0.--OH i=1 of 2; Y= ##STR17## R₁ =lower alkyl, aryl, substitutedalkyl, substituted aryl, lower alkoxy, aryloxy, or mixtures thereof;G=--SO₂ --, --S--, --CH₂ --, or --O--; j=0, 1, or 2; n=an integer suchthat the oligomer has an average formula weight of between about 1,000to about 40,000; Me=methyl; T=allyl or methallyl; and .0.=phenyl.
 2. Theblended oligomer of claim 1 wherein the polymer is a polyethersulfone.3. The blended oligomer of claim 1 wherein having substantiallyequimolar proportions of the oligomer and polymer.
 4. The blendedoligomer of claim 1 further comprising a suitable coreactant.
 5. Aprepreg comprising the blended oligomer of claim 1 and a reinforcingadditive in fiber or particulate form.
 6. A composite formed by curingthe prepreg of claim
 5. 7. A prepreg comprising the blended oligomer ofclaim 4 and a reinforcing additive on fiber or particulate form.
 8. Amultidimensional polyethersulfone oligomer prepared by reacting anaromatic hub having at least three reactive --OH functionalities with adihalogen selected from the group consisting of:X--.0.--q--.0.--X,X--.0.--O--.0.--q--.0.--O--.0.--X, X--.0.--q--.0.--.0.--.0.--q--.0.--X,or X--.0.--SO₂ --.0.--SO₂ --.0.--SO₂ --.0.--Xand an imidophenol end-capmonomer of the general formula Y_(i) --.0.--OH wherein Y= Y= ##STR18##R₁ =lower alkyl, aryl, substituted alkyl, substituted aryl, loweralkoxy, aryloxy, or mixtures thereof; G=--SO₂ --, --S--, --CH₂ --, or--O--; j=0, 1 or 2; R=an aromatic radical; R'=an aromatic radical; n=aninteger such that the oligomer has an average formula weight of betweenabout 1,000 to about 40,000; i=1 or 2; Me=methyl; T=allyl or methallyl;X=halogen; .0.=phenyl; and q=--S--, --SO₂ --, --CO--, --(CH₃)₂ C--, or--(CF₃)₂ C--.
 9. The oligomer of claim 8 further comprising the residueof a dialcohol between residues of dihalogen.
 10. A blend comprising theoligomer of claim 8 and a compatible, noncrosslinking polymer.
 11. Aprepreg comprising the oligomer of claim 8 and a reinforcing additive infiber or particulate form.
 12. A composite comprising the cured prepregof claim
 11. 13. A prepreg comprising the blend of claim 10 and areinforcing additive in fiber or particulate form.
 14. A blendcomprising the oligomer of claim 8 and a suitable coreactant.
 15. Amethod for making a polyethersulfone multidimensional oligomercomprising the step of condensing an aromatic polyol hub molecule of thegeneral formula Ar-OH)_(w) wherein Ar=an aromatic radical and w=aninteger greater than or equal to 3 with a dihalogen, a bisphenol, and acrosslinking imidophenol in a suitable solvent under an inertatmosphere.
 16. A method for making a polyethersulfone multidimensionaloligomer comprising the step of condensing an aromatic polyhalide of thegeneral formula Ar-X)_(w) wherein Ar=an aromatic radical, X=halogen, andw=an integer greater than or equal to 3 with a bisphenol, a dihalogen,and a crosslinking imidophenol in a suitable solvent under an inertatmosphere.